All the varied types that belong to the simian family are, in the common order of speech, known as _monkeys_, but the term thus used is so broad in its meaning as to include all the forms of that vast group, wherefore it is vague and obscure, for some of these resemble man more than they resemble each other. The name should only be applied to those having tails and short faces, but there is a small group, which have no tails at all, that are properly known as _apes_. While they are all simians, they are not all monkeys. It is with this small group, without tails, that we propose chiefly to deal. We select them because of their likeness to man, and having noted the similitude, the result may be compared with other types of the same order. There are only four of these apes, but as a whole they resemble man in so many essential details that they are called "anthropoid," or "man-like apes." They differ from each other in certain respects, almost as much as any one of them differs from man. The four apes alluded to, are the chimpanzee, the gorilla, the orang and the gibbon. As the skeleton is the framework of the physical structure, it will serve as the basis upon which to build up the comparison, and as the chimpanzee is the nearest approach to man, we select him as the highest type of the simian, and use him as the standard. The skeleton of the chimpanzee may be said to be exactly the same as that of man, but the assertion must be qualified by a few facts which are of minor importance, but since they are facts we cannot ignore them. The general plan, purpose and principle are the same in each. There is no part of the one that is not duplicated in the other, and there is no function discharged by any part of the one that is not discharged by the like part of the other. The chief point in which they differ is in the structure of one bone. Near the base of the spinal column is a certain bone called the _sacrum_. It is a constituent part of the column, but in its singular form and structure somewhat differs from the corresponding bone in man. The general outline of this bone in the plane of the hips is that of an isosceles triangle. It fits in between the two large bones that spread out towards the hips, and articulate with the thighbones. [Illustration: PELVIS OF CHIMPANZEE A Sacrum. B Fourth lumbar vertebra. C Coccyx. D Ilium or hip-bone. E Femur or thigh-bone. ] About half-way from the centre to the edge, along each side, is a row of four round holes. Across the surface of the bone is a dim transverse line between each pair of holes, from which it appears that five smaller sections of the column have anchylosed or grown into each other to form the _sacrum_, and the holes coincide with the open spaces between the lateral processes of the other bones of the column above.